Alternating current track circuit with direct current track relay superimposed thereon



March 31, 1959 ALTERNATING CURRE P N MAR N Original Filed April 15, 1952 1) I62 1 1r" 1 I I j 50 55 05 -11 -10 1b 24/ l 4 334 25' EAR DAB 26 F 5915 R4 R1 H'lzwa T 2 M DB 5 21 5 5 1g g Signal U D7731 BX XX 52 [VX 27 Signai avnflol y 54 ;E C'ZICLZCZ.

INVENTOR.

H16 Aawomvzr United States Patent ALTERNATING CURRENT TRACK CIRCUIT WITH DIRECT CURRENT TRA'CK RELAY SUPERIM- POSED THEREON Paul N. Martin, Wayne, Pa., assignor to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Original application April 15, 1952, Serial No. 282,405. Divided and this application August 24, 1954, Serial No. 451,824

2 Claims. (Cl. 246-64) My invention relates to alternating current track circuits with direct current track relays super-imposed there on, and more particularly to an alternating current railway track circuit having a direct current track relay controlled thereby and provided with a track battery as a standby source for energizing the track relay when the alternating current source fails.

The present application is a division of my copending application, Serial No. 282,405, filled April 15, 1952, for Alternating Current Track Circuits with Direct Current Track Relays Superimposed Thereon, now abandoned.

In railway wayside signal systems alternating current track circuits are used extensively. Frequently these track circuits are coded by being periodically interrupted at different code rates to reflect difierent trafiic conditions. At many points along railways using such signaling systems, it is necessary to provide for automatic control of highway crossing signals and gates, the automatic control of the highway crossing gates and signals being obtained through the track circuits. In these signal systems in which an additional control for highway crossing signals is required from the track circuit, the apparatus can be simplified if a track relay can be operated at each end of the track circuit for the track section in the approach to a highway crossing. Furthermore, when highway crossing gates or barriers are used, it is necessary to have a control such that the highway gate or barrier is not held in a position that stops highway trafiic in case of a failure of the alternating current source normally supplying the track circuit. It is also a requirement in some highway crossing signal installations, due to the high speeds of the trains, .to provide for operation of the warning signals while a train is traversing more than one track section in approach of the crossmg.

In view of these circumstances in railway signaling systems, an object of my invention is the provision of an alternating current railway track circuit incorporating novel means whereby a direct current track relay is superimposed thereon in such a manner that two track relays, one at each end of the corresponding track section, are energized from a single source of alternating current.

Another object of my invention is the provision of an alternating current railway track circuit having a direct current track relay superimposed thereon and incorporating an auxiliary or standby direct current source for energizing the direct current track relay in the cause of a failure of the alternating current source.

Also, an object of my invention is the provision of an alternating current track circuit with a direct current track relay controlled thereby and incorporating means vfor further controlling the direct current track relay from the next track circuit in approach.

Patented Mar. 31, 1959 Other features, objects, and advantages of my invention will appear as the specification progresses.

The foregoing objects, features and advantages of my invention I attain by the provision of a novel and improved combination of track circuit apparatus which includes a circuit network having, in effect at least, a power source and a track relay at each end of the associated track section.

I shall describe one form of apparatus embodying my invention and shall then point out the novel features thereof in claims.

The accompanying drawing is a schematic view of one form of railway track circuit apparatus embodying my invention.

Referring to the drawing, the reference characters 1a and 1b designate the track rails of a stretch of railway track over which traffic normally moves in the direction indicated by the arrow. These rails are formed in the usual manner into an insulated track section DE which may be one section of a series of consecutive sec tions of an automatic signal system. The track section DE would be of a length found suitable for such a signal system.

The section DE is provided with a track circuit which includes the track rails in series and, in effect, a source of power and a track relay connected across the rails at each end of the section. At the entrance end D of the section, that is, the left-hand end as viewed in the drawing, there is provided an alternating current track relay DTRl and a track battery DB. Relay DTRl and battery DB in series are normally connected across the section rails over lead wires 10 and 11, an adjustable resistor R3 being preferably interposed in lead wire 11. A front contact of a relay DAR is also interposed in this series circuit. The utility of this contact will be described shortly. However, during the preliminary description of the operation of the apparatus, this front contact will be considered to remain closed.

The alternating current track relay DTRl may take different forms. For simplicity, it is herein shown as a two-element alternating current relay having one element 34 connected directly to terminals BX and NX of the power source and a second element 35 connected across the rails of the section in series with track battery DB, one terminal of relay element 35 being connected to rail in by lead wire 10 and its other terminal connected to rail 112 through battery DB, front contact 36 of relay DAR, resistor R3, and lead wire 11. An alternate path, discussed hereinafter, is provided for this element 35 of the relay around battery DB, the alternate path including a resistor 37 and back contact 36 of relay DAR.

An asymmetric unit, such as a half wave copper oxide rectifier element 18, for example, and an adjustable resistor R4 in series are connected across lead wires 10 and 11, this circuit path through the asymmetric unit being in multiple with the path through the track battery DB and the alternating current track relay in series. Another front contact of relay DAR, to be discussed hereinafter, is interposed in this circuit path but for the present is considered to remain closed. The asymmetric unit 18 is poled to substantially block the direct current from track battery DB. It follows that asymmetric unit 18 substantially blocks the half cycles of alternating current of the track circuit that cause rail 1b to be positive with respect to rail 1a, but presents little resistance to the flow of current in the half cycles of the alternating voltage that rail 1a is positive with respect to rail 112, it being understood that resistor R4 is of relatively low resistance. It is also to be noted that battery DB is poled for its positive and negative terminals to be as indicated by the plus and minus signs placed on the drawing.

At the exit end B ofsection D--E, that is, the righthand end as viewed in drawing, the track circuit apparatus includes a source of alternating current and a direct current tra'ck'frfelay Lginf multiple.

The "immediate source of talternating current for the track circuit is a secondary winding 21 of a track transformer ET, a primary winding 19 of which is connected to an alternating current power supply source. The secondary winding 21 has one terminalconnected to rail 1a over lead wire 22, and its, other terminal connected to rail 1b by a reactor 23, resistor R1, and lead wire 24. The alternating current power source may be any suitable source although in general practice it is a remote generator and a transmission line circuit mounted on a pole line extending along the railway right of way. This alternating current source is not shown for the sake of simplicity and is indicated in the drawing by the reference characters BX and NX which designatefthe two terminals of the alternating current source. Preferably, the alternating current frequency would be 100 cycles per second since such frequency is used extensively in railway signal systems, but other frequencies can be used. I, As shown and described in the now abandoned parent application Serial No. 282,405, the alternating current supplied to the track circuit may be coded at difierent code rates. The use of such coded track current is contemplated by the present application but is not shown in the drawing for the sake of simplicity, such circuit to such alternating current.

With alternating current being supplied to the track circuit, considernow the period that the half cycles of the alternating current are of such polarity that rail 1a is positive with respect to rail 1b. through asymmetric unit 18 at this time includes the unit 18 in its forward or conductive direction so that this path is of a relatively low resistance. Also, the path through battery DB and winding of alternating current track relay DTRl includes the battery inits polarity aiding direction 'so that this path also is of relatively low resistance to these half cycles of the alternating current. Hence these half'cycles of the alternating current are substantially shunted away from direct current track relay EAR at the exit end E of the section. During the half cycle of the alternating current that rail 1b is positive with respect to rail 1a, the path through asymmetric unit 18 includes the unit in its reverse or high resistance direction and the current is substantially blocked from flowing through this path. .The path 'through track battery DB and winding 35 of relay DTRl includes the battery in its polarity opposing direction and the current is substantially blocked except during the portion of the alternating voltage wave that exceeds in magnitude the voltage of the battery. This means that during the half cycles of the alternating voltage in which rail 1b is positive, relay EAR will be en ergized, whereas during the other half cycles, as has been shown, the current is efiectively shunted away from it. Relay EAR, having relatively large inductance, operates entirely satisfactorily on this pulsating type of energization. Consequently, when track section DE is unoccupied, track relay EAR is energized by unidirectional current caused by the rectifying action of unit 18 and alternating current track relay DTRl is energized by the portion of each half cycle of the alternating current that flows in winding 35.

If coded alternating current is being used, during the The circuit path off code periodof the track circuit current when no alternating current pulse is supplied to the track rails, relay EAR receives no current from the alternating current source. Relay EAR may be provided with slow release characteristics to retainits energization from one code pulse to the next. However, it is observed that during the off code'period of the track circuit current, direct current will flow from battery DB through the track circuit to the winding of relay EAR and that relay is energized by'the current supplied from the track battery. The direction of the flow of current through the winding of relay EAR from the track battery is the same as that of the rectified current so that the relay will remain picked up.{ For this reason therelay EAR may not be required to be provided with slow release characteristics.

In the track circuit shown, the parts are proportioned so that with the alternating current power disconnected the resistor R3 is adjusted for track relay EAR to receive proper working current from track battery DB under'the minimum-ballast resistance conditions. Then with the alternating current power connected to the track circuit and resistor R4 shunted, the track transformer secondary winding 21 is adjusted to provide a voltage sufiicient to effectively energize alternating current track relay .DTRI aunder the minimum ballast resistance. Ilnder jtheseadjustments, trackbattery DB will supply some current to the track circuit for energizing relay EAR under low ballast resistance conditions as well as during any period that the alternating current power is off. .I-lowever, asymmetric unit 18 will cause the alternating current source to supply a rectified current nearly -suflicient to energize relay EAR. Also, a portion of each cycle of the alternating current will be supplied to winding 35 and relay DTRl will pick up. It is to be noted that in. energizing alternating current track relay DTRl, track battery DB exerts a voltage that tends to aid the flow of current in one direction and opposes the flow in the other direction.

I When the ballast is dry and of a relatively high resistance, the alternating voltage appearing across the rails of the track circuit increases and asymmetric unit 18 causes the direct current component of the track circuit voltage to be larger than the voltage of battery DB so that a small current flows through the battery in the direction to charge or recondition it. This reconditioning of battery DB compensates for some, at least, of the drain on the battery under low ballast resistance, during periods when the alternating current is off, and when the rails are shunted by a train occupying the section. This reconditioning of the track battery is desirable to provide a relatively long battery life, especially when a primary battery is used. The reconditioning current can be regulated by adjustable resistor R4.

Hence, with the track section unoccupied, track relay DTRl'is energized by the track circuit current and its contact 27 is operated. Contact 27 can be used to control signal circuits of any standard form, not shown, for

controlling in turn a wayside signal, such as the signal DS located at the entrance end of the section to govern trafiic through the section. Also, relay EAR at the exit end of the section is picked up closing its front contact 26. This contact can be used to control highway crossing gates and signals located at a highway, such as highway i H illustrated as intersecting the railway in the vicinity of the exit end of section DE. When a train enters section DE and shunts the track rails, both track relays DTRl and EAR will be deenergized and release. With relay DTRl released, the wayside signal D5 will be controlled to a stop position. With relay EAR released opening front contact 26, the highway crossing gates and signals at the highway H are operated to a warning position indicating the'approach of the train.

It is clear that in case the source of alternating current BXNX fails, track =battery DB will function as a standby source and provide current for energizing track relay EAR when the section is unoccupied, the relay releasing when the track circuit is shunted by a train entering the section. Thus, the control of any highway crossing gate or signal by relay EAR will be undisturbed and continued in the proper manner in the event the alternating current fails.

in track circuits of the type here involved, it is frequently necessary to provide an approach control for the highway signals for more than a single track section in advance without disturbing the normal railway signal control arrangement. Thus, in the drawing, the control that is provided by the direct current track relay for control of the highway crossing gates and signals at the highway H is relayed at the entrance end D of section DE to provide additional approach control for the highway crossing protection.

At the entrance end D of section DE, there is shown that portion of the apparatus, for the track circuit for the section next in the rear of section DE, that corresponds to the track circuit apparatus provided at the exit end E for section D--E. That is, the location D is the exit end of the section next in the rear as Well as being the entrance end of section DE. Thus at this location there is provided apparatus similar to the apparatus shown at location E for the track circuit of section DE. This apparatus at location D associated with the track circuit next in the rear includes a track transformer DT and a track relay DAR, which in multiple are connected across the section rails. Specifically, a primary winding 32 of transformer DT is connected to terminals BX and NX of the alternating current power source. A secondary winding 33 of the transformer has one terminal connected to rail 1b by reactor 28, resistor RlA, and lead wire 30, and its other terminal connected to rail 1a by lead wire 31. Relay DAR has its winding connected to lead Wires 30 and 31 through a resistor RZA.

Normally, that is, when section D-E and the section next in the rear are unoccupied, track relay DAR is picked up closing front contacts 36 and 38 and the track circuit apparatus for section D-E effectively energizes relay EAR in part by the rectified current caused by asymmetric unit 18 and in part by the current supplied by battery DB, as hereinbefore explained. Also alternating current track relay DTRl is energized by the alternating current component of the track circuit current supplied to the element 35 of that relay.

When a train enters the section next in the rear of section D-E, relay DAR is shunted and releases in the same manner that relay EAR is shunted and releases when a train enters section DE. The opening of front contacts 36 and 38 of relay DAR interrupts the supply of unidirectional current to relay EAR and that relay releases, opening its front contact 26 to initiate the warning operation of any highway crossing protection device that may be controlled by relay EAR. With relay DAR released closing back contact 36, the element 35 of alternating current relay DTRI is connected across the rails through the resistor 37. Relay DTRI thus continues to be energized by the alternating current component of the track circuit current. When the train advances and enters section DE, the element 35 is shunted and relay DTRl releases and controls any wayside signal that may be controlled thereby, relay EAR being shunted and retained deenergized.

Although I have herein shown and described but one form of alternating current track circuits with direct current track relays superimposed thereon embodying my invention, it is to be understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a section of railway track formed in a stretch of railway through which trains move in a given direction; a first track circuit arrangement including the rails of said section, a source of alternating current connected across said rails at the exit end of said section, and an alternating current track relay, a track battery, and a transfer contact connected in series across said rails at the entrance end of said section, said battery being included in said series connection when the front point of said transfer contact is closed and being bypassed when the back point of said transfer contact is closed; a second track circuit arrangement including said section rails, said alternating current source, a direct current track relay connected across said rails at said exit end, and an asymmetric unit and a front contact in series connected across said rails at said entrance end, said unit being poled to block How of current from said battery through said unit; said alternating and said direct current relays being normally energized by said alternating current source through said first and said second track circuit arrangements respectively when said section is un occupied, and control means for said transfer and said front contacts having connections to the rails in a selected portion of said stretch in approach to said section to be responsive to the occupancy condition of said selected portion, said control means effective to hold said front contacts closed when said selected portion is unoccupied by a train, said control means releasing said front contacts when a train occupies said selected portion to interrupt said second track circuit arrangement and closing said back contact to maintain operative said first track circuit arrangement.

2. In combination with a first and a second section of railway track over which trafiic moves from said second section into the adjacent first section, a direct current track relay, a source of alternating current, said source and said direct current relay connected in multiple across the rails at the exit end of said first section, an alternating current track relay, a track battery, said battery and said alternating current track relay connected in series across the rails at the entrance end of said first section, an asymmetric unit connected across the rails at said first section entrance end in multiple with the series connection at that location and poled to block the flow of current from said battery through said unit, both said direct current relay and said alternating current relay being normally energized by said source when said first section is unoccupied, another track relay connected across the rails at the exit end of said second section, another source of current connected across the rails of said second section to normally energize said other track relay, said other track relay becoming deenergized when said second section is occupied by a train, front contacts of said other track relay interposed in each path of the multiple connections at said entrance end of said first section to interrupt the connections through said unit and said battery and thus deenergize said direct current relay when said second section is occupied, and a back contact of said other track relay interposed in the connections at said entrance end of said first section in series with said alternating current relay to bypass said front contacts and maintain said alternating current relay energized until a train occupies said first section.

References Cited in the file of this patent UNITED STATES PATENTS 1,791,838 Pelikan Feb. 10, 1931 1,914,958 OHagan June 20, 1933 2,393,135 Agnew Jan. 15, 1946 

